The present invention relates to a travelling-wave tube with a delay line section and an electron collector, comprising several electrodes, which is arranged inside a hollow cylindrical metal cooling chamber having one end surface or wall which is connected in vacuum-tight manner to the end of the delay line section and which has a diameter which is larger than the diameter of the delay line section.
Multi-stage collectors, i.e. electron collectors having several collector electrodes lying one behind the other in the direction of electron beam in order to achieve an improved degree of efficiency, are already known in travelling-wave tubes.